US2561004A

US2561004A - Method and apparatus for grinding

Info

Publication number: US2561004A
Application number: US112708A
Authority: US
Inventors: John C Wilson; William G Baldenhofer
Original assignee: Thompson Grinder Co
Current assignee: Thompson Grinder Co
Priority date: 1949-08-27
Filing date: 1949-08-27
Publication date: 1951-07-17
Anticipated expiration: 1968-07-17

Description

July 17, 1951 J. c. WILSON 'ETAL n 2,561,004 f METHOD AND APPARATUS FOR GRINDING Filed Aug. 27, 1949 9 Sheets-Sheet l 9 1 N NVENTORS JOHN C. W/LSO/V N B WILL/AM `C. BlEl/HOFER ATTOPNE YS UY 17, 1951 J. c. WILSON ET AL. 2,551,004

METHOD AND APPARATUS FOR GRINDIG July 17, 1951 J. c.kwn soN E'TAL METHOD AND APPARATUS FOR GRINDING 9 Sheets-Sheet 5 J Filed Aug. 27, 1949 /NVE/V7'OR6 JOHN C. W/LSON WILL/AM 0. BALDENHOFEE E July 17 1951 `.1. c. wlLsoN ETAI. v 2,561,004

` M Emop AND APPARATUS Foa @RINO-ING y Filed Aug. 2v, 1949 .B-SheetS-Sheet 4 @awww ATTORNEYS.

July 17, 1951 J. C. wlL-soN ETAL METHOD AND APPARATUS FOR GRINDING 9 Sheets-Sheet 5 Filed Aug. 27, 1.949

July 17, 1951 J. c. wlLsoN ETAL l 2,561,004

METHOD AND APPARATUS FOR GRINDING Filed Aug. "27, 1949 f 9 sheets-sheet e "VA w4- y JMAJW July 17, 1951 J. c. wlLsoN ETAL METHOD AND APPARATUS FOR GRINDING Filed Aug. 27, 1949 9 sheets-sheet 'f /NvENToRs from/vs m S M W C N M d July 17, 1951 l J. c. wlLsoN ETAL 2,561,004

METHOD AND APPARATUS FOR GRIND'ING Filed Aug. 27, 1949 9 Sheets-Shed'l 8 WEA/fors fof/N 0. w/so/v WILL/AM 0. BALDE/w/offe ,7am fw@ July 17, 1951 J. C. WILSON `ET AL METHOD AND APPARATUS FOR GRINDING 9 Sheets-Sheet 9 Filed Aug. 27, 1949 START OF GRINDING CYCLE k m uw m z CRUSH DRESSING CYCLE (R w 5%. mi /nf y /D Mw W C. B 4c, /MC- 0M PJM l. MJ .wn E R U s s E R D.. NL A wm. me P E M P NE um@ SCW E RTDY USF-L nbHvDnDl SAF-D. EHTAW RXE PEM PEP Patented July 17, 1951 UNITES @ENCE RJETHUD AND APPARATUS FOR GRINDNG John C. Wilson and William G. Baldenhofer, Springeld, (Ehio, assignors to The Thompson Grinder Company, Springeid, Gino, a corporation ol Ohio Application August 27, 1949, Serial No. 112,708

(Cl. 51-84l) l5 Claims. l

This invention relates to grinding machines and to methods of operation thereof, and particularly to grinding machines having a plurality of grinding wheels for grinding a plurality of different surfaces of a workpiece simultaneously. A great many workpieces have more surfaces to be nished thereon than can be ground by a single wheel at one time. Heretofore, it has been customary to have as many different grinding operations on such a workpiece as there were different surfaces to be finished and, inasmuch as this required a different set-up for each operation, a great many errors resulted, 'leading to improperly shaped or incorrectly sized workpieces. Q

Other attempts have been made to arrange a machine with a plurality of wheels thereon so that two or more surfaces of a workpiece of this nature could be ground at one time. This substantially reduced the number of set-ups required to finish the workpiece and accordingly resulted in a more economical process, and one in which there was less chance for the workpieces to be improperly shaped.

However, grinding wheels must frequently be dressed in order to maintain their conguration between predetermined allowable limits for obtaining properly shaped workpieces. With the arrangement described immediately above, the proper dressing of the wheels was found to be very diflicult. This was due to the fact that the wheels were independently dressed and the relative positions of the grinding surfaces of the wheels following dressing was not always exactly correct.

The particular type workpiece for which the machine of the instant invention was developed brings out clearly the difficulties encountered in connection with machines of the prior art. This workpiece is a bucket or blade for the turbine of f a jet engine and must be machined to highly accurate limits. The workpiece is symmetrical about a center line and its opposite faces must be ground to congurations which are in exact conformity with each other and also in exact i alignment with each other.

A particular object of this invention is the provision of an improved grinding machine arrangement for grinding workpieces of the nature referred to, and a method of operating the may chine to effect the said grinding.

Another object of this invention is the pro- Vision of a grinding machine, and a method of operating the same, utilizing a plurality of grinding wheels and characterized in that the said 2 wheels are always in exact and rigid alignment.

A still further object of this invention is the provision of a multiple Wheel grinding machine in which the said wheels can be adjusted independently or in unison to eiect the grinding of opposite faces of a work piece.

Another object of this invention is the provision of a multiple wheel grinding machine for operating different faces of a workpiece at one time and which machine is substantially smaller than machines constructed according to the prior art.

It is also an object of this invention to provide a grinding machine having multiple wheels, a workpiece station and a dressing station so constructed and arranged that the wheels and stations are prevented from getting out of alignment.

rfhese and other objects and advantages will become more apparent upon reference to the following description taken in connection with the accompanying drawings in which:

Figure l is a iront View or a machine constructed according to this invention and with a portion of the bed of the machine broken away to show some of the operative parts;

Figure 2 is a plan View looking down the top of the machine and with the cover plate removed from the right-hand wheel-head slide to show the arrangement of the parts therein;

Figure 3 is somewhat enlarged plan view looking down on top or the center part of the machine and showing somewhat more in detail the work` piece and the dresser supporting carriage and the actuating mechanism therefor;

Figure 4 is a vertical section indicated by line l-li on Figure 3 and showing somewhat in detail the construction or" the work piece supporting slide and dresser supporting slide;

Figure 5 is a vertical section indicated by line 5-#5 on Figure 2, and showing in detail the construction of the wheel-head supporting slide;

Figures 6, 7 and 8 are section views indicated respectively by lines JL-ii, l-TL and 8-8, on Figure 5,'

Figure 9 is a somewhat enlarged view looking in at the iront of the work piecesupporting slide, showing the construction thereinc and the limit means for controlling its travel;

Figure 10 is a plan section indicated by line iii-id on Figure 4i, and showing the construction oi the dresser supporting slide;

Figure ll is an enlarge view or' `a typical work piece adapted for being treatec in a machine oi this invention with the grinding wheels of the 3 machine shown on opposite sides of the work piece; and

Figures 12, 13 and 14 are diagrammatic views showing the operation of one of the wheel slides.

General arrangement A machine constructed according to this invention generally comprises a bed having slidably mounted thereon a pair of wheel-head slides with grinding wheels mounted on the wheel-head slides for movement toward and away from each other by movement of the said slides. These grinding wheels have grinding surfaces arranged in alignment on opposite sides of the space between the Wheels.

Slidably mounted on the bed is a carriage movable in a direction generally parallel with the axes of rotation of the grinding wheels. This carriage carries a work piece supporting unit and a dresser supporting unit and is adapted for selectively positioning said units in alignment with the grinding wheels. When so positioned in alignment with the Wheels, the units can be reciprocated vertically on the carriage for carrying out the operative functions of the members supported thereon.

' According to this invention, the dresser unit is preferably a crush forming roll and the described arrangement insures that the grinding surfaces of the wheels will at all times exactly conform with each other and be in exact alignment because they are dressed by a single dressing roll.

Also, according to this invention, a diamond dresser is provided for one of the wheels, and when this one wheel is dressed by the diamond dresser, it is then utilized for grinding the dressing roll, with the other wheel being driven at low speed to act as a feed or regulating wheel for the crushing roll.

To accommodate for Wheel wear and for changes in size of the dressing roll, the machine includes adjustments for selectively adjusting the positions of the grinding wheels relative to each other and relative to the bed of the machine.

Structural Arrangement Referring to the drawings somewhat more in detail and particularly Figures 1 through 3, the grinding machine illustrated therein comprises a bed 20, having a central part 22 and side or end parts 24. Upstanding from the end parts 24 are the spaced guide or rib members 26 and these members 26 on one end part of the bed are in exact and rigid alignment with those on the other end part of the bed.

Reciprocably mounted on the guide members 26 on each of the end parts of the bed is a wheelhead slide 28, mounting at its end toward the center part of the bed a wheel-head motor 30 carrying a grinding wheel 32. As will be seen in Figure 2, the wheels 32 are coplanar and are rotatable on parallel axes: but it will be evident, as the description of this invention proceeds, that the wheels 32 can be angularly arranged relative to each other, if so desired, the essential thing being that each of the wheels 32 has an angular grinding surface thereon which is in alignment with the corresponding surface of the other wheel.

Extending across the central part of the bed at right angles to the direction of the movement to the wheel-head slides 28, is a pair of spaced rods 34. The extreme ends of rods 34 are supported in the front and back walls of the bed as will be seen in Figure 3. The cap members 36 may advantageously be employed for effecting this support.

The rods 34 are provided for guiding a carriage member 38 which has the laterally projecting parts 40 encircling the rods 34 and preferably journalled on the said rods by the bearing sleeves 42.

Due to the fact that considerable grit and other abrasive matter is thrown o from the grinding station of the machine, the carriage 38 and rods 34 are preferably provided with bellowslike protective boots 44 that prevent any part of the said rods which the bearing sleeves 42 engage from ever being exposed to the atmosphere.

The carriage 38 carries a workpiece supporting unit 46 at its one end and intermediate its ends carries a dresser supporting unit 48 and the carriage is adapted for selectively moving the said units into operative alignment of the grinding wheels 32. In the arrangement illustrated, where the wheels are co-planar, the workpiece unit is in operative alignment with the wheels when the workpiece 50 carried thereby is co-planar with the wheels.

Similarly, the dressing unit 48 is in operative alignment with the grinding wheels when the dresser roll 52 carried thereby is co-planar with the said wheels.

The movement of the carriage member 38 between its two operative positions is accomplished by means of a cylinder 54 mounted on the carriage and a double acting ram 56 in the cylinder having the end of its rod part secured to the rear wall of the bed 20, as indicated at 58. Fluid is supplied to the left end of cylinder 54 for moving carriage 58 leftwardly, by conduit 60 which communicates through the said ram by means of passage 62 therein with the said left end of the cylinder. Similarly, the carriage is moved rightwardly by introduction of pressure fluid into the right end of cylinder 54 by conduit B4.

It will be understood that any suitable valve means could be provided for controlling the supply of uid to, and the exhaust of fluid from, the opposite ends of cylinder 54. Preferably, the limits of movement of carriage 33 are determined by stop means within cylinder 54. Thus, when the carriage is in its right-hand position as shown at Figure 3, abutment means E6 provide a stop for said carriage, while in its left-hand position carriage 38 is stopped by abutment of piston 53 with abutment member 68 in the said cylinder.

Turning now to Figure 4, this view when taken with Figure 3 will reveal the detailed construction of the carriage and slides thereon. The aforementioned workpiece supporting unit 46 comprises a table part 'it supporting any suitable type of workpiece engaging fixture 12, the particular details of which are of no importance in connection with this application other than the said fixture provides a rigid and solid support for the workpiece.

Table Hl is mounted on the upper end of a cylinder 14 which is slidably guided on the left end of the carriage member 38 by the flanges 16, projecting outwardly from the cylinder and fitting into grooves 18 in the end of the carriage member. Gib members are fastened to cylinder 14 and clamp the said flanges slidably in position in the said grooves. Preferably, a plurality of auxiliary tapered gibs are provided for holding flanges 16 snugly in grooves 18 so that cylinder 74 is rigidly guided for vertical reciprocation at all times.

Extending vinto `cylinder V:'hi'is a double acting ram 84, .including the rod :part B6 that is clamped at one vend of afbracket., mounted on the bottom of carriage tmember 38, as by screws '90. lRam 84 is vadapted :for abutment f-withzspa'ced stop members 'S2 which provide Alimits for the travel of cylinder 'I4 vertically relative to `said carriage member. Fluid is :selectively supplied to opposite .ends of -cylinder""|'4 bythe 'conduits 94and 9.5, these conduitsbein-g .connected to .any suitable valve arrangement.

Reference 'to Figure 9 ywill `reveal that cylinder y'I4 includes a slotted iia-nge 58 that :adjustably receives a pair of cams .itil and 1'82 'adap-tedfor engagement with limit lswitches 1:04 and |06. Normally, these l-imitswitches determine the extent -of tra-vel of cylinder 54, :andthe above referred to stop members 52 are operative only if cylinder i4 over-travels itsproper limits.

Dresser unit 48 is best illustrated vin Figures i and 1-0 wherein 'it will be seen that there is mounted in carriage member .38 a member |58 den-ning a substantially square bore and comprising the two rparts ||J .and ,||2, vwhich are doweled and bolted to the Vcarriage member as will be seen in Figure 10. vertically reciprocable within the member |08, .is la square member |l4 having a bore HS that reciprocably receives double acting ram ||8 having rod part"|2|| connected with the rear end offbracket 83.

Square member 4 :is urged into iirm'engagement with machined flats on the sides of member |58 by tapered gib elements |22. The arrangement is such that the dresser unit is guided for vertical reciprocation relative to carriage member i58 and is rmly and rsolidly supported at alltimes.

For reciprocating member 4, fluid may be admitted to the upper end 'of cylinder bore H6 from conduits |24 through bore "|26 extending through ram H8, or tothe lower end of Said bore by -conduit |28, the said conduits being connected to any suitable valvi-ng means.

The upper end of square member ||4 includes a table |38 von which is mounted a housing |32 that rotatably supports a shafton which the crusher roll 52 is mounted. The portion of member |44 which extends upwardly out .of square cylinder |58 may be protected lby the boot arrangement |34, if desired.

Duo to the weight of `the carriage and the units thereon and the working thrusts exerted on the units, auxiliary support is ,provided for rods 34 intermediate their ends by the bed supported screws 55. The provision Aoi these `screws prevents deflection of the said rods beyond allowable limits and insures accurate positioning of the carriage in the vertical direction at all times.

Turning now to Figures 5 through 8, the righthand wheel-head slide 28 is .shown in detail. The wheel-head slide comprises an upper or main slide |40 directly supjz-iorted -on rib members 25, as b-y the balls |42. Preferably the balls run .in V-ways vcarried by the main slide member, and the upstanding ribs and tapered -gi-b `arrangement |44 provides for the taking up of all play between .the said `V-ways and balls.

Main slide |453 is hollow and therein is mounted a member |55 generally Uashaped in Vplan and having a dependent side part |48 that denes a dovetail opening for receiving a dovetail slide member |50. The dovetailslid'e member |50 is a secondary or subslide and .is moveably relative to the main slide on the aforementioned dovetail slide arrangement.

Lead screw |64 is journalled in bed 2|) as at |66 and is connected by a coupling |68 with a shaft |10 mounted in the bed at the left-hand end of the lead screw. Shaft Ilo mounts a gear |74 and this gear is adapted for being vdriven by a Shaft |16 having on its inner end gear |18 meshing with gear |14., and vhaving its outer end a hand wheel arrangement which may be manually actuatedy or Which may be automatically actuated, according to practices well known in the art.

The piston |58 is mounted in a frame compris-- ing end plates |85 and tie rods |81. The right end plate |35 extends .upwardly `and mounts an adjustable stop member consisting of stationary sleeve part and screw |92 .adjustable therein. Preferably, screw |52 is graduated as at |94 and there is a clamp screw |96 for locking screw |92 in any predetermined .position of adjustment. The inner end of screw |92 is adapted for engagement with abutment member |98 :on the right-.hand face of sub-slide |55. It will be apparent that the stop referred to previously, consisting of the right-hand vface of piston |58 and the inner surface of the adjacent end cap |55, and the stop provided .by abutment les and screw |92, predetermine the 'limits of relative .movement of sub-slide |50 `and piston |58.

Mainslide IIdil yalso mounts, internally thereof, a cylinder 20|) into which extends double act-ing ram 262 that has the end oi its rod part secured to subslide |50 as by bracket t will .be apparent that introduction of pressure fluid into one end or the other of cylinder 2M, as through conduits 256. will bring about relative ymovement between main slide .|40 and subnsl-ide |50. One limit of this movement is determined by the abutment member 208 in cylinder 205 that abuts ram 252, while the other limit is determined by abutment 2|0 mounted on sub-slide 511| and adjustable stop screw 2 |2 at the right end of main slide |40. Adjustable stop screw Z|2 is constructed similarly to the previously described stop screw arrangement associated with the sub-'slide and nut and can be locked in any position of adjustment.

As mentioned previously, one of the grinding Wheels is arranged to be dressed by a diamond dresser. To this end one grinding wheel slide has a mounting platform 2id thereon on which is mounted a contour type diamond dressing unit 25|). The particular construction of the dia-mond dressing unit forms no part of the instant invention and it will be understood that any suitable arrangement for forming the proper contour on the grinding wheel would be satisfactory.

During the cr-ush dressing of `the 4Wheels rby dresser -roll 52 the said wheels and roll are turned at low speed so :the crushing roll will crush 'the wheels to the proper configuration, as is well known in the art of crush forming grinding wheels. For the purpose of driving the wheels and roll at dressing speed, one thereof is provided with a low speed motor. This is illustrated in Figure 2 at 2|8, and is a geared head motor adapted for driving through the over-running clutch 220 into the shaft supporting the grinding Wheel on the left-hand side of the machine.

Operation In operation, work pieces to be ground are placed in proper position on table and carriage member 33 is moved to its rear-most position, thereby carrying the workpieces into co-planar alignment with the grinding wheels. At this time the main slide U of each of the wheel-head slides occupies its inner position with stop screws 2|2 abutting abutments 2|0 of the sub-slides. The sub-slides at this time occupy their outermost positions with their abutment means |08 abutting the inner ends of stop screws |92. The spacing between the wheels with the slides so disposed is then the proper distance for commencing the grinding of the workpieces.

Grinding is then started by reciprocating the workpiece slide a supply of pressure uid to cylinder 'M thereof.

Many workpieces can be ground in a single pass between the wheels, but others are preferably ground by taking a number of passes between the wheels and adjusting the wheels inwardly on each pass until the workpiece is brought down to the proper size. The method to be preferred will be determined by the nature of the workpieces being operated and, in general, multiple passes will be used when it is desired not to overheat or stress the piece being ground, and single pass, or plunge grinding will be used where the workpiece will not be harmed by such rapid removal of stock.

When workpieces are ground according to the multiple pass method, the pistons |53 and cylinders |52 are availed of to feed the wheels inwardly toward the workpieces. This is accomplished by incrementally metering fluid into the left-hand ends of the said cylinders, whereby the sub-slides |50 move away from their outer stopped positions inwardly toward the center of the machine and carry with them the main slides |40 on which the grinding wheels are mounted.

It will be evident at this time that the amount of movement each sub-slide |50 can have relative to its associated piston |58 is determined by the adjustment of the associated stop screw |92. Each of the said sub-slides will move from its outer stopped position inwardly until its piston is abutted by the outer one of end caps |56 as explained previously. Accordingly, the stop screws |02 are adjusted so the total amount of movement slides |50 can have relative to their pistons is exactly equal to the depth of cut to be taken from each face of the workpieces being ground. This is based on the assumption, of course, that the wheels are positioned at the surface of the workpiece when slides |40 are in and sub-slides |50 are out.

It will be apparent that the grinding of workpieces consists merely of mounting them on the workpiece supporting unit, then moving slide member 38 into grinding position, and then vertically reciprocating the workpiece supporting slide. This operation can be repeated as many times as desired for grinding a plurality of workpieces.

When it becomes desirable, or necessary, to redress wheels 32, the slides |40 and |50 are moved to their outermost positions. In their outermost stopped positions, the slides support the wheels the proper distance apart for being crush formed by the dressing roll 52. This dressing is accomplished by rst positioning the wheels as described and de-energizing motors 30 so that the wheels come to a halt.

The dresser supporting unit slide is then raised to its uppermost position. This places the axis of the crushing roll above the axes of grinding wheels and the slide member 38 can then be moved forwardly of the machine to dressing position with the crushing roll 52 co-planar with the grinding wheels 32, but in spaced relationship with both of the said wheels.

The dresser unit slide is then moved downwardly to bring the roll into pressure engagement with the grinding wheels and motor 2|8 is energized to drive the left-hand wheel at low speed. With the roll 52 in pressure engagement with both of the grinding wheels, the driving'of the one wheel is effective for causing the wheels and roll to roll together, thereby carrying out a dressing operation on the said wheels. When the dresser unit slide has moved downwardly until the axis of the dresser roll is co-planar with the axes of the grinding wheels, the dressing cycle is completed. Thereafter, the dresser unit slideis again moved vertically to disengage the roll from the wheels, and normal grinding operations can again be resumed in the manner described previously.

Inasmuch as a certain amount of material is removed from each wheel when it is dressed, the wheel-head slides must be adjusted inwardly either before or during a dressing cycle. This is accomplished by rotating the lead screws |64 either by hand or by any suitable automatic means to give the proper amount of inward movement of said slides.

It will be noted that the adjustment of lead screws in no way affects the amount of travel that the slides |40 and |50 can take, Adjustment of the lead screws merely shifts the slide units inwardly to compensate for the amount of material taken from the wheels during dressing so that when grinding is resumed the wheels will bev properly positioned to grind the required amount from the workpieces being operated.

At more or less frequent intervals the dresser roll 52 will become worn beyond allowable limits and must be restored to shape for further dressing. According to this invention, the diamond dressing unit 2|6 is then availed of for shaping right-hand wheel 32. This is done according to priactices well known in the diamond dressing ar After right-hand wheel 32 has been exactly shaped by the diamond dresser, the wheel is utilized for grinding the dresser roll. This is done by bringing the roll into pressure engagement with left-hand wheel 32 as though carrying out a dressing cycle and driving the said wheels by low speed motor 2|8. The pressure with which the roll is brought against the wheel, however,

is not suicient to cause a crushing action, but is suiiicient to cause the wheel to drive the roll in rotation. With the roll being so driven the diamond trued wheel is driven at grinding speed and is brought into grinding relation with the said dressing roll.

A relatively light grinding operation on the roll, during which time it makes several revolutions, is generally sufficient for restoring the roll to proper conguration and it can thereafter beutilized for crush dressingcycles', as previously described.

Inasmuch as a certainamount ofy material has been removed from the right-hand wheel by the action of the diamond dresser and .a vcertain amount of material yis ground from thedressing roll 52, it is necessary to make adjustments in the relative positions of the wheel slides and. the stop screws between the slides. For example, the amount of material removed from the righthand wheel during the diamond dressing thereof can be compensated for byadjusting its lead screw 64 independently of the lead screw for the-other slide. The amount of material removed from the dressing roll is compensated for by adjusting both of the lead screws I 64 to move the slides inwardly thev amount removed from the.v crushing roll. Also, the abutment screws 2|2 are ad.- justed inwardly the same amount so that after the wheels have been crush formed by the roll, the slides |40 will have the proper amount of travel to carry the wheels inwardly a distance equal to the diierence between the radius of the dressing roll and the width of the workpiece on one side of the center line thereof.

To summarize the operation of the machine briefly, a grinding operation comprises vertically reciprocating workpieces between the wheels: a dressing operation comprises vertically reciprocating the dressing roll between the wheels: and the trueing of the dressing roll is done by diamond dressing one of the wheels and utilizing it to grind the roll while the other wheel drives the roll in rotation.

Reference to Figure 11, at this time will show one type of workpiece adapted for being treated in the machine of this invention. In Figure 11, the workpiece is indicated at 250 and it will be seen to comprise a tapering part having series of ridges on each face. The wheels 32 have congurations thereon conforming to the configuration of the workpiece' and it will be evident that workpieces of this nature can be formed to very close limits and with the opposite sides in perfect alignment with each other by utilizing the machine and method of this invention.

Figures 12, 13 and 14 diagrammatically illustrate the movements of one of the wheel-head slides. In Figure 12, the sub-slide |50 is in its outer stopped position while the main slide I 40 is in its inner stopped position. This places the grinding wheels in position to engage the surface of workpiece 50 for the rst pass thereacross.

In Figure 13, the wheel head slide is shown at the completion of a grinding cycle and it will be noted that the main slide |40 is still in its inner stopped position while sub-slide |50 has moved to its inner stopped position. This last mentioned movement is accomplished by the supply of metered increments of pressure uid to the left end of the cylinder bore in which piston |58 is movable.

It will be noted in Figure 13, that the workpiece has been reduced in size on each side of the center line by an amount exactly equal to the amount of movement which the sub-slide |50 has between its two stopped positions.

In Figure 14, the wheel slide is shown in position for a crush dressing cycle and both the main slide |40 and the sub-slide |50 occupy their outer stopped positions. The crush forming roll is moved downwardly between the wheels with the amount of material that is desired to dress from the periphery of the wheels being determined by adjustment of lead screws |64.

Figures 12, 13 and 14 have been more or less diagrammatically drawn with some ofthe parts shown, and the distances which they move, eX- aggerated in. order to provide a clear picture of theoperation of the slide.. Also, certain explanatory legends and dimensions'have been applied to-those views for simplifying the reading thereof.

It will be understood that. many other shapes ofl workpieces areadapted for beingground .according to this invention and vthat in sor'necases, as-forexampla when the` faces to be ground were widely divergent, it might be necessary to arrangethe grinding wheelslangularly relative to each other rather than copllanar, as has been shown.and described.A However, the principles of this invention obtain. fully in connectionwith that type of modication-.

It has been pointed vout that the dressing roll, or one of the grindingv wheels, might be operated at-lowfspeed during-the crush dressing cycle and also during the grinding of the dressing roll.. This lowfspeed drivehas been shown as associated with one of the grinding wheels, but it will be understoodk that the roll could be so driven, if desired, or necessary, or that both the roll and the wheels could be provided with low speed drives.l

No reference has been made inthis application to any particular type of operatingor control arrangement for controllingthe operation of the several fluidA an'delectric motors illustrated. Itis believed thatvoneskiilled in the art-could supply-such a control system'.I It willi be understood that, in general, the operation of the machineis automatic as. by solenoid operated valves and contactors, and that a suitable control panel including push-button stations and-the like could be associated therewith forv controlling the entire operation of the lmachine of this invention.

It will be understood that this invention is susceptible-to modification in order to adapt it to different usages and conditions, and, accordingly', it is desired-'to comprehend such modifications within this invention asm-ay fallk within the scope of the appended claims.

We cla-im:

1. 1inv a grinding machine; a bed, a pair of grinding wheels supported on said bed, said wheels being spaced and having grinding surfaces there'- on running in alignment on opposite sides of the space therebetween the axes of rotation of said wheels being co-planar, a carriage movable at an angleto the direction of alignment of said surfaces and in= a plane midway between said axes; a dressing unit and a workpiece supporting unit movable on said carriage in said plane and adapted' for selective operative alignment with said" wheels by movement ofv said carriage', means for movingsaid wheels relatively on said bed to vary` the distance therebetween', and means for moving said carriage' and units to place' workmembers on the'units in operative alignment with said wheels'.

2. InY a grinding machine; a pair of grinding wheels, said- Wheels being spaced and having grindingl surfaces thereon running in' alignment on opposite sides of the space between the wheels, a carriage movable at an'angle to the direction of alignment of said surfaces, a dressing unit and a workpiece supporting unit movable on said carriage at an angle to both the direction of movement of the carriage and the direction of alignment: of the wheel surfaces, means for moving said carriage for selectively aligning said units with saidV wheels, and means for moving said "units on said carriage'to c'arry the work mem- 'on opposite sides of the space between the wheels,

a carriage movable at right angles to the direction of alignment of said surfaces, a dressing unit -and a workpiece supporting unit on said carriage,

means for moving said carriage for selectively aligning said units with said wheels, and means for moving said units on said carriage to place vthe work members carried thereby in operative engagement with said wheels.

4;,In a grinding machine; a pair of grinding wheels, said wheels being spaced and having grinding surfaces thereon'running in alignment on opposite sides of the space between the wheels, a carriage movable at right angles to the direction of alignment of said surfaces, a dressing unit and a workpiece supporting unit on said carriage, means for moving said carriage for selectively aligning said units with said wheels, means for moving said units on said carriage to place the work members carried thereby in operative engagement with said wheels, and means for moving said wheels toward and away from each other to vary the space therebetween.

5. In a grinding machine: a bed, a pair of spaced grinding wheels rotatable on parallel axes on said bed, said wheels having grinding surfaces aligned on opposite sides of the space between the wheels a carriage slidably supported on said bed for movement parallel with said axes, a dressing unit and a workpiece supporting unit carried by said carriage for movement in a direction at right angles to said axes, means for moving said wheels toward and away from each other, and means for effecting the movements of said carriage, said units, and said wheels to carry out a dressing cycle during which the wheels are simultaneously dressed, and a grinding cycle during which two faces of the workpiece are simultaneously ground. p

6. In a grinding machine; a bed, a pair of co-planar grinding wheels on said bed rotatable on parallel axes, a carriage on said bed slidable in a direction parallel with said axes, a workpiece supporting unit on said carriage reciprocable perpendicularly to the plane of said axes to carry a workpiece thereon into the space between the wheels for a grinding operation on opposite sides of the workpiece, a dressing unit on said carriage also reciprocable perpendicularly to the plane of said axes to carry a dressing member thereon into the space between the wheels for a dressing operation on both wheels simultaneously, and slides supporting said wheels for movement toward and away from each other.

7. In a grinding machine: a bed, a pair of coplanar grinding wheels on said bed rotatable on parallel axes, a carriage on said bed slidable in a direction parallel with said axes, a workpiece supporting unit on said carriage reciprocable perpendicularly to the plane of said axes to carry a workpiece thereon into the Space between the wheels for a grinding operation on opposite sides of the workpiece, a dressing unit on said carriage also reciprocable perpendicularly to the plane of said axes to carry a dressing member thereon into the space between the wheels for a dressing operation on both wheels simultaneously, vand. slides supporting said wheels for movement toward and away from each otherl said slides hav- 12 ing stopped inner and outer positions, and means for adjusting said positions. v

8. Ina grindingy machine, a pair of grinding wheels having grinding surfaces aligned on opposite sides of the space therebetween and having their axes of rotation coplanar, a crush dressing roll rotatable on an axis parallel to said plane, means for spacing said wheels a distance apart a predetermined amount less than the diameter of said roll, means for moving said roll in a direction perpendicular to said plane into the space between said wheels, means for rotating said wheels and roll together atthe same peripheral speed, and means urging said roll toward a position where its axis is co-planar with the axes of said wheels.

9. In a grinding machine; a pair of spaced coplanar grinding wheels having grinding surfaces aligned on opposite sides of the space therebetween and rotatable on coplanar axes, a crush dressing roll rotatable on an axis parallel to said plane, means for spacing said Awheels a distance apart a predetermined amount less than the diameter of said roll, means for moving said roll perpendicular to said plane into the space between said wheels means for rotating said wheels and roll together at the same peripheral speed, and means urging said roll toward position where its axis is coplanar with the axes of said wheels with a substantially constant thrust.

l0. In a grinding machine; a pair of spaced ccplanar grinding wheels rotatable on parallel axes, a crush dressing roll rotatable on an axis parallel to the grinding wheel axes, means for spacing said wheels a distance a predetermined amount less than the diameter of said roll, means for moving said roll into the plane of said wheels with the axis of the roll spaced from the plane of the axes of the wheels, fluid operable means for thrusting said roll in the plane of the wheels toward a position where all of said axes are coplanar, and means for causing said wheels and roll to roll together for simultaneously crush dressing both of said wheels at one time.

1l. In a grinding machine: a bed comprising spaced upstanding ribs, a rst slide slidably supported on said ribs, a second slide slidably supported by said first slide, said second slide comprising a cylinder depending therefrom into the space between said ribs. a piston in said cylinder, a screw supported in said' bed between said ribs and screw threadedly engaging said piston, a fluid operable motor connected between said slides, and abutment means between said slides, and between said second slide and piston to limit the amount of rela-tive movement between the slides and ben tween the second slide and piston.

l2. In a grindingymachine: a bed, a nrstslide slidably sup-ported on said bed, a second slide slidably supported by said first slide, said second slide comprising a cylinder, a piston in said cylinder, a screw in said bed engaging said piston, a fluid operable motor connected between said slides, land abutment means between said slides and between said second slide 4 and piston to predetermine limits of movementfof ysaid slides.

13. In combination; `a, lead screw, a slide to be driven by the lead screw, a cylinder carried by the slide and surronndingthe screw, a piston in the cylinder threaded on said` screw,v saidpiston being formed in tivo parts and the said parts each being threaded on said screw, and means for clamping said parts xedly together in any position of relative-angularl adjustment. y y l le. A method ci dressing grinding. wheels for simultaneously grinding opposite faces of a Workpiece comprising: supporting a pair of grinding Wheels with their grinding surfaces spaced and in alignment, moving a crush forming roller of greater diameter than the space between the wheels toward the said space in the plane of the wheels into pressure engagement with the wheels, rotating the wlieeis and roll together, and moving the roll to a position where its axis is coplanar with the axes of the said wheels.

15. A method of grinding a workpiece so the opposite sides are in exact conformity with each other comprising; supporting a pair of grinding Wheels with their grinding surfaces spaced and in alignment, positioning the wheels in xed radially spaced outer positions, moving a crush forming roller of greater diameter than the space between the wheels toward said space in the plane of the wheels into pressure engagement with the Wheels, rotating the wheels and roll together, moving the roll to a position where its axis is coplanar with the axes of said wheels, removing the roll from between said wheels, passing a workpiece between the wheels in the plane of the wheels, and moving the wheels toward each other to xed inner positions.

JOHN C. WILSON. WILLIAM G. BALDENHOFER.

REFERENCES CITED The following references are of record in the iile of this patent:

Number Number UNITED STATES PATENTS